CN115274238A - MnBiAl permanent magnetic alloy with high magnetic energy product and preparation method thereof - Google Patents

MnBiAl permanent magnetic alloy with high magnetic energy product and preparation method thereof Download PDF

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CN115274238A
CN115274238A CN202210840729.4A CN202210840729A CN115274238A CN 115274238 A CN115274238 A CN 115274238A CN 202210840729 A CN202210840729 A CN 202210840729A CN 115274238 A CN115274238 A CN 115274238A
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alloy
mnbial
permanent magnetic
preparation
energy product
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陆伟
陆顺达
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Tongji University
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Tongji University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/0302—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity characterised by unspecified or heterogeneous hardness or specially adapted for magnetic hardness transitions
    • H01F1/0306—Metals or alloys, e.g. LAVES phase alloys of the MgCu2-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]

Abstract

The invention discloses a MnBiAl permanent magnetic alloy with high magnetic energy product and a preparation method thereof, wherein the MnBiAl permanent magnetic alloy comprises Mn55Bi45‑xAlxWherein x is more than 0 and less than or equal to 4. The preparation method comprises the following steps: an alloy ingot was prepared using a vacuum induction melting technique, followed by annealing at 290 ℃ for 12 hours. According to the invention, by doping a proper amount of Al element, the Al element occupies Bi atoms and vacant sites of MnBi crystal, the lattice parameters of the Al element are optimized, the ferromagnetic coupling between Mn and Mn is regulated, the magnetocrystalline anisotropy is improved, the permanent magnetic property of the alloy is finally regulated, and the maximum magnetic energy product of the alloy material is greatly improved after the test; the preparation process is simple and easy to implement, and has great application prospect.

Description

MnBiAl permanent magnetic alloy with high magnetic energy product and preparation method thereof
Technical Field
The invention relates to the technical field of permanent magnet materials, and relates to a MnBiAl permanent magnet alloy with a high magnetic energy product and a preparation method thereof.
Background
In recent years, permanent magnetic materials are widely applied to electromagnetic devices, motors, sensors and other equipment as key materials for conversion of electric energy, magnetic energy and mechanical energy. At present, the permanent magnet market mainly comprises a ferrite permanent magnet material with low price and a rare earth permanent magnet material with excellent performance. The ferrite permanent magnet material has the advantages of low price, good stability and the like, but the application of the ferrite permanent magnet material in miniaturization and lightweight device equipment is limited by the lower magnetic energy product. Rare earth permanent magnet materials have excellent permanent magnet properties, but their wide application is limited by the increasingly depleted and expensive rare earth resources. In addition, in order to improve the high-temperature performance of the rare earth permanent magnet material, expensive heavy rare earth elements are added into the alloy components, so that the cost of the rare earth permanent magnet material is inevitably and greatly increased. Therefore, under the dual standards of performance and cost, the development of a permanent magnetic material with low price and performance between that of ferrite and that of rare earth permanent magnetic material is urgently needed.
The Mn-based permanent magnet material is concerned by the characteristics of low price, excellent performance and the like. In particular, the MnBi permanent magnet alloy has a large magnetic energy product, a high coercive force and a positive coercive force temperature characteristic. The unique performance makes the high-temperature-resistant composite material applied to high-temperature fields such as hybrid electric vehicles, wind driven generators and the like. Therefore, the MnBi permanent magnetic alloy is one of the most potential rare earth-free permanent magnetic materials at present. However, the maximum energy product of the MnBi alloy is much smaller than its theoretical value. The maximum energy product of the MnBi alloy is mainly related to remanence and coercivity. The MnBi low-temperature phase is generated through peritectic reaction between Mn element and Bi element, and the Mn element is easy to oxidize and segregate in the solidification process, so that the formation of the MnBi low-temperature phase is inhibited, and the saturation magnetization and the remanence of the MnBi alloy are low. The coercive force can be increased by refining the crystal grains by means of ball milling or the like, but also the decomposition of the MnBi low-temperature phase is caused.
Therefore, how to ensure a higher saturation magnetization while increasing the coercivity is a problem that needs to be studied urgently.
Disclosure of Invention
Due to the defects in the prior art, the invention provides a MnBiAl permanent magnetic alloy with high magnetic energy product and a preparation method thereof.
In order to achieve the purpose, the invention provides the following technical scheme:
the MnBiAl permanent magnetic alloy with the high magnetic energy product comprises Mn55Bi45- xAlxWherein x is more than 0 and less than or equal to 4.
According to the invention, by doping a proper amount of Al element, the Al element occupies Bi atoms and vacant sites of MnBi crystals, the lattice parameters of the Al element are optimized, the ferromagnetic coupling between Mn and Mn of the Al element is regulated, the magnetocrystalline anisotropy is improved, the permanent magnetic property of the Al element is finally regulated, and the maximum magnetic energy product of the alloy material is greatly improved after testing.
The invention also provides a preparation method of the MnBiAl permanent magnetic alloy with high magnetic energy product, which comprises the following steps:
(1) According to the composition Mn55Bi45-xAlxPreparing raw materials, wherein x is more than 0 and less than or equal to 4;
(2) Fully melting the raw materials obtained in the step (1) under the protection of inert gas, and cooling to obtain an alloy ingot;
(3) Crushing the alloy ingot obtained in the step (2), and remelting for multiple times to obtain a remelted alloy ingot;
(4) And (4) carrying out heat treatment on the remelted alloy ingot obtained in the step (3) to obtain the MnBiAl permanent magnetic alloy, wherein the heat treatment is carried out for 10-14 h at 275-325 ℃ under a vacuum condition.
Because a large amount of precipitated manganese phases and residual bismuth phases exist in the alloy ingot prepared by induction melting and the ferromagnetic MnBi low-temperature phase content is low, the alloy ingot is subjected to vacuum heat treatment to further obtain more low-temperature phases MnBi.
The preparation process is simple and easy to implement, strong in feasibility, mild in conditions and low in cost.
As a preferred technical scheme:
in the above-mentioned manufacturing method, the melting and remelting are performed in a vacuum induction melting furnace.
The preparation method described above, the step (2) is specifically:
putting the raw materials obtained in the step (1) into a crucible of a vacuum induction melting furnace, and vacuumizing the melting furnace to 10 DEG-3And (3) introducing high-purity argon below Pa, heating to fully melt the raw materials (slowly increasing induction current), keeping the temperature for 10min, and pouring into a water-cooled copper mold to prepare an alloy ingot.
According to the preparation method, the crucible is made of high-purity boron nitride.
In the preparation method, in the step (3), the remelting frequency is more than 3 times so as to improve the uniformity of the alloy components.
The preparation method comprises the following steps of preparing high-purity manganese sheets, bismuth ingots and aluminum particles with the purity of not less than 99.97 percent as raw materials;
the actual addition amount of the high-purity manganese sheet is 8wt% more than the theoretical addition amount, which is to compensate the volatilization of manganese element in the smelting process. 8wt% is determined according to experimental results, and the specific process is as follows: firstly, respectively taking the theoretical addition amounts of Mn and Bi elements, smelting, annealing, taking small blocks for EDS analysis, obtaining element content information including the atomic ratio and the weight ratio of the Mn element and the Bi element, and comparing the element content information with a theoretical value (Mn: bi = 55).
The production method as described above, wherein the heat treatment is carried out in a vacuum tube furnace;
the heat treatment specifically comprises the following steps: pumped by molecular pump to vacuum degree of 10-5Pa, then raising the temperature from room temperature to 290 ℃ at the temperature raising rate of 5 ℃/min, preserving the temperature for 12 hours, and then slowly cooling along with the furnace after the heat preservation is finished.
The preparation method as described above, further comprising:
(5) And (4) crushing and grinding the MnBiAl permanent magnetic alloy prepared in the step (4) into powder, and screening by using a mesh screen to obtain MnBiAl permanent magnetic alloy powder.
In addition, the remelted alloy ingot can be cleaned before the remelted alloy ingot is subjected to heat treatment (specifically, the surface of the remelted alloy ingot is polished, and the remelted alloy ingot is repeatedly subjected to ultrasonic cleaning and drying in absolute ethyl alcohol).
The preparation method as described above, wherein the mesh number of the mesh screen is 1000 meshes;
the particle size of the MnBiAl permanent magnet alloy powder is not more than 13 mu m.
The above technical solutions are only one possible technical solution of the present invention, the protection scope of the present invention is not limited thereto, and those skilled in the art can reasonably adjust the specific designs according to actual needs.
The invention has the following advantages or beneficial effects:
according to the invention, by doping a proper amount of Al element, the Al element occupies Bi atoms and vacant sites of MnBi crystal, the lattice parameters of the Al element are optimized, the ferromagnetic coupling between Mn and Mn is regulated, the magnetocrystalline anisotropy is improved, the permanent magnetic property of the alloy is finally regulated, and the maximum magnetic energy product of the alloy material is greatly improved after the test; the preparation method is simple and easy to implement, strong in feasibility, mild in condition, low in cost and extremely wide in application prospect.
Drawings
The invention and its features, aspects and advantages will become more apparent from reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Like reference symbols in the various drawings indicate like elements. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
FIG. 1 is a non-isothermal DSC curve of the phase transitions of remelted alloy ingots of examples 1-4 and comparative examples;
FIG. 2 is an XRD pattern of the products obtained in examples 1 to 4 and comparative example;
FIG. 3 is a hysteresis loop at room temperature of products obtained in examples 1 to 4 and a comparative example;
FIG. 4 is a graph showing the change of saturation magnetization, coercive force, and maximum magnetic energy product with the increase of Al content for the products obtained in examples 1 to 4 and comparative example.
Detailed Description
The structure of the present invention will be further described with reference to the accompanying drawings and specific examples, but the present invention is not limited thereto.
Example 1
Mn (manganese)55Bi44Al1The preparation method of the permanent magnet alloy powder comprises the following steps:
(1) Manganese, bismuth and aluminum with the purity of not less than 99.97 percent are taken as Mn according to nominal components55Bi44Al1Preparing an alloy raw material, and adding 8wt.% more Mn in consideration of the volatilization of Mn element;
(2) Putting the raw materials prepared in the step (1) into a boron nitride crucible in sequence, placing the boron nitride crucible into an induction coil in an induction smelting furnace, and carrying out smeltingThe furnace chamber is vacuumized to make the vacuum degree reach 10-3Pa, closing the vacuum pump, filling a proper amount of high-purity argon into the chamber, then slowly increasing the induced current until the alloy is completely molten, preserving the temperature for 10min, pouring the alloy into a water-cooled copper mold, and taking out an alloy ingot after full cooling;
(3) Crushing the alloy ingot obtained in the step (2) into small pieces, putting the small pieces into the crucible again, remelting the alloy ingot, wherein the remelting process is the same as the operation in the step (2), and repeatedly remelting the alloy ingot for 3 times to improve the uniformity of alloy components;
(4) Placing the remelted alloy ingot obtained in the step (3) into a corundum crucible, placing the corundum crucible into a vacuum tube furnace for heat treatment, and vacuumizing by adopting a molecular pump to ensure that the vacuum degree in a quartz tube reaches 10-5Pa, then heating from room temperature to 290 ℃ at the heating rate of 5 ℃/min, preserving heat for 12 hours, and slowly cooling along with the furnace after the heat preservation is finished to obtain an alloy ingot after heat treatment;
(5) Crushing the alloy ingot obtained in the step (4) after heat treatment, fully grinding the crushed alloy ingot into powder by using a mortar, and passing the powder through a 1000-mesh stainless steel mesh screen to ensure that the particle size of the powder is not more than 13 mu m, thereby finally obtaining Mn with uniform particle size55Bi44Al1And (3) alloying powder.
Example 2
Mn (manganese)55Bi43Al2A process for producing a permanent magnet alloy powder, which is substantially the same as in example 1, except for the amount of raw materials added, which is the same as Mn55Bi43Al2The proportion of (c) is matched.
Example 3
Mn (manganese)55Bi42Al3A process for producing a permanent magnet alloy powder, which is substantially the same as in example 1, except for the addition amount of the raw materials, which is the same as Mn55Bi42Al3The proportion of (c) is matched.
Example 4
Mn (manganese)55Bi41Al4A process for producing a permanent magnet alloy powder, which is substantially the same as in example 1, except for the addition amount of the raw materials, which is the same as Mn55Bi41Al4The proportion of (c) is matched.
Comparative example
Mn (manganese)55Bi45A process for producing a permanent magnet alloy powder, which is substantially the same as in example 1, except for the amount of addition of the raw materials which do not contain Al and Mn55 Bi45The proportion of (c) is matched.
The products from examples 1 to 4 and comparative example were tested as follows:
(A) The thermal phase transition behavior of the remelted alloy ingots obtained in examples 1 to 4 or in step (3) of the comparative example was measured by Differential Scanning Calorimetry (DSC).
(B) The microstructure, phase composition and lattice parameters of the permanent magnet alloy powders obtained in the step (5) of examples 1 to 4 or the comparative example were measured by X-ray diffraction analysis (XRD).
(C) The magnetic properties at room temperature of the permanent magnet alloy powders obtained in examples 1 to 4 or step (5) in the comparative example were measured using a Vibrating Sample Magnetometer (VSM).
The test results are specifically as follows:
in order to illustrate the effect of Al element doping on the thermal phase transition behavior of MnBi alloy, the samples prepared in examples 1-4 and comparative example were thermally analyzed by the present invention, and the obtained DSC curve is shown in FIG. 1. Analysis shows that the second endothermic peak in the DSC curve gradually shifts to high temperature along with the increase of Al content, which indicates that the phase transition temperature of the MnBi low-temperature phase is increased, so that the Al element doping improves the thermal stability of the MnBi low-temperature phase.
In order to illustrate the influence of Al element doping on the microstructure of MnBi alloy, the samples prepared in examples 1 to 4 and comparative example were subjected to X-ray diffraction analysis according to the present invention, and the obtained XRD patterns are shown in fig. 2, and the phase compositions and lattice parameters of the samples are shown in table 1 below. Analysis shows that Al element doping causes decomposition of the MnBi low-temperature phase to some extent, but increases the axial-to-radial ratio (c/a) of the MnBi low-temperature phase, and increases magnetocrystalline anisotropy.
TABLE 1 tables of phase composition and lattice parameter of samples obtained in examples 1 to 4 and comparative example
Figure BDA0003750934720000071
In order to illustrate the effect of Al element doping on the magnetic properties of MnBi alloys, the present inventors performed magnetic property tests at room temperature on the samples prepared in examples 1 to 4 and comparative example, and obtained hysteresis loops as shown in FIG. 3.
In addition, in order to more intuitively reflect the influence of the doping of the Al element, fig. 4 lists the variation curves of the saturation magnetization, the coercive force, and the maximum magnetic energy product with the increase of the Al content. As can be seen from the analysis, when the Al element content is 1at.%, the magnetocrystalline anisotropy is most significant, and the most excellent overall magnetic properties are exhibited. Mn (Mn)55Bi44Al1Saturation magnetization (M) of permanent magnet alloy powder measured in an applied magnetic field of 3Ts) 71.7emu/g, coercive force (H)c) Is 10.7kOe, maximum energy product ((BH)max) Was 12.6MGOe relative to Mn in the comparative example55Bi45The comprehensive magnetic performance of the sample is improved by 18 percent, which shows that the maximum magnetic energy product of the MnBi alloy can be obviously improved by doping Al element.
In conclusion, the invention obviously improves the maximum magnetic energy product of the MnBi alloy by doping a proper amount of Al element in the MnBi alloy, shows excellent comprehensive magnetic performance and has important significance for further development and wide application of the MnBi alloy.
It should be understood by those skilled in the art that the above embodiments may be combined with the prior art to realize the modifications, and the detailed description is omitted here. Such variations do not affect the essence of the present invention and are not described herein.
The above description is of the preferred embodiment of the invention. It is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments to equivalent variations, without departing from the spirit of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are within the scope of the technical solution of the present invention, unless the technical essence of the present invention is not departed from the content of the technical solution of the present invention.

Claims (10)

1. A MnBiAl permanent magnetic alloy with high magnetic energy product is characterized in that: the MnBiAl permanent magnetic alloy consists of Mn55Bi45-xAlxWherein x is more than 0 and less than or equal to 4.
2. A preparation method of MnBiAl permanent magnetic alloy with high magnetic energy product is characterized by comprising the following steps:
(1) According to the composition Mn55Bi45-xAlxPreparing raw materials, wherein x is more than 0 and less than or equal to 4;
(2) Fully melting the raw materials obtained in the step (1) under the protection of inert gas, and cooling to obtain an alloy ingot;
(3) Crushing the alloy ingot obtained in the step (2), and remelting for multiple times to obtain a remelted alloy ingot;
(4) And (4) carrying out heat treatment on the remelted alloy ingot obtained in the step (3) to obtain the MnBiAl permanent magnetic alloy, wherein the heat treatment is carried out for 10-14 h at 275-325 ℃ under a vacuum condition.
3. The method of claim 2, wherein the melting and remelting is accomplished in a vacuum induction melting furnace.
4. The preparation method according to claim 3, wherein the step (2) is specifically:
putting the raw materials obtained in the step (1) into a crucible of a vacuum induction melting furnace, and vacuumizing the melting furnace to 10 DEG-3And introducing high-purity argon below Pa, heating to fully melt the raw materials, and pouring into a water-cooled copper mold to prepare an alloy ingot.
5. The method according to claim 4, wherein the crucible is made of high purity boron nitride.
6. The production method according to claim 2, wherein in the step (3), the number of remelting is 3 or more.
7. The production method according to claim 2, wherein the raw materials are high-purity manganese flakes, bismuth ingots and aluminum particles having a purity of not less than 99.97%;
the actual addition amount of the high-purity manganese sheet is 8wt% more than the theoretical addition amount.
8. The method according to claim 2, wherein the heat treatment is performed in a vacuum tube furnace;
the heat treatment specifically comprises the following steps: pumped by molecular pump to vacuum degree of 10-5Pa, then raising the temperature from room temperature to 290 ℃ at the temperature raising rate of 5 ℃/min, preserving the temperature for 12 hours, and then slowly cooling along with the furnace after the heat preservation is finished.
9. The method of claim 2, further comprising:
(5) And (4) crushing and grinding the MnBiAl permanent magnetic alloy prepared in the step (4) into powder, and screening by using a mesh screen to obtain MnBiAl permanent magnetic alloy powder.
10. The method of claim 9, wherein the mesh number of the mesh screen is 1000 mesh;
the particle size of the MnBiAl permanent magnet alloy powder is not more than 13 mu m.
CN202210840729.4A 2022-07-18 2022-07-18 MnBiAl permanent magnetic alloy with high magnetic energy product and preparation method thereof Pending CN115274238A (en)

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